An Embedded Optical Signature (EOS) can be added to a lottery scratch-off ticket as, for example, an image under the scratch-off coating. The EOS validation data revealed from under the removed scratch-off coating can then be processed with the ticket's barcode data (not hidden under a scratch-off coating) allowing the ticket to be validated without any other action required from the person initiating the transaction. An EOS can also be used to ensure the authenticity of a printed document, such as an on-line lottery ticket, provide copyright protection, or carry additional information such as the name and address of an individual filling out a form.
To process an EOS from a document (e.g., scratch-off lottery ticket, on-line lottery ticket, receipt, bet slip, etc.), a scanner or camera is generally necessary to capture a digital image of the document. An inexpensive camera, linear sensor, or contact image sensor may be used to provide this image capture functionality. However, certain problems may be encountered in such applications.
For example, whether attempting to capture an EOS or other information on a printed document, a scanner should preferably be able to capture the relevant data without interference from the surrounding environment. Linear or Contact Image Sensors (CIS) typically include a mechanical mechanism that either moves the document past the sensor or vice versa. One method of isolating the scan head from environmental light contamination is to provide intrinsic illumination in a darkened environment. However, with this type of system, traces of dirt or debris on the scan head can create a significant amount of image noise because the scan head only captures one dimension of the image with the movement of the document/scan head providing the other dimension. FIG. 1 illustrates this problem with scan 100 being of a blank document with small particles of dirt on the scan head and scan 105 showing the same document with a clean scan head. This susceptibility to dirt-induced noise makes this type of scanner disfavored for dirty environments such as, for example, the processing of scratch-off lottery tickets. Additionally, if a questionnaire or bet slip is completed with a ballpoint pen and a sufficient amount of time is not allowed for the ink to completely dry, ink can transfer to the scan head and create this type of dirt-induced noise in linear/CIS scanners. Additionally, the reliability of a mechanical scanning mechanism is inherently worse than a fully electronic device.
Two-dimensional camera scanners can minimize the effects of dirt and ink noise while increasing reliability by eliminating the need to physically move the document or scan head. Additionally, mounting the camera some distance away from the target document creates an open space that isolates the camera lens from the dirt/ink noise sources. If the camera is placed above a platen, the dirt and ink noise problem can be further reduced because a fresh document is presented for each scan with no visible residual dirt left on a scanning surface or glass platen if the document is scanned face up. Unfortunately, the spacing of the camera above a platen allows direct-reflection-noise (i.e., glare) to be introduced from ambient light or poorly positioned scanner lighting sources. Referring to FIG. 2, image 200 shows a scratch-off lottery ticket with ambient glare while image 205 shows a scratch-off lottery ticket without ambient glare. Image 210 shows a camera image of a scratch-off lottery ticket with glare from internal lighting while image 215 shows the same lottery ticket without glare from internal lighting.
Glare noise from ambient light sources can be eliminated by encasing the camera scanner mechanism in a light tight enclosure. However, opening a door or moving a curtain may be cumbersome and slow for an operator. Careful placement of light sources can also eliminate scanner-internal glare noise. As illustrated in FIG. 3A, glare is eliminated or reduced as light sources 300 are moved into non-reflection areas 305. FIG. 3B shows a camera view of a platen 320 with a light source about 2 inches above on both sides while platen 325 has a light source and diffuser about 2 inches above on both sides such that less glare is apparent on the platen. FIG. 4 illustrates the light intensity relative to the x-y location on a platen with various locations for the light sources. For example, graph 400 represents a platen with side illumination sources 1 inch above the platen, graph 405 represents a platen with side illumination sources 2 inches above the platen, graph 410 represents a platen with side illumination sources 4 inches above the platen, and graph 415 represents a platen with side illumination sources 5 inches above the platen As illustrated in FIGS. 3A, 3B and 4, moving the light sources further away from the platen greatly improves the side to side illumination uniformity and substantially improves front to rear illumination uniformity, but requires significantly more space for the scanner housing. Additionally, mounting a camera above a platen and not securing the document to a flat plane introduces a potential new error source if the document is bowed. More specifically, variability in the distance between the scanned surface and the camera can introduce a locational error that limits the size of symbols.
Trapezoidal error is introduced if the camera is not mounted perfectly parallel to the plane of the platen. If a mirror is added in an attempt to reduce the size of the scanner housing, proper alignment becomes even more critical because any alignment error will be magnified by a factor of two.
Finally, a camera and platen based scanning system is susceptible to errors caused by the human operator improperly aligning the document on the platen. This problem is less of an issue with motorized one-dimensional scanners (e.g., CIS) since the motor can be used to help align the document.
Therefore, while two-dimensional camera scanning can virtually eliminate dirt and ink induced noise and increase the reliability of the scanner (i.e., no moving parts), such a design can introduce its own sources of scanning errors, which can become increasingly irksome as the target document grows in size. New scanner designs capable of processing large documents (for example, questionnaires, large instant tickets with EOS, or bet slips with smaller decision grids) would be particularly advantageous. Accordingly, the present disclosure provides alternatives by which the performance of a camera and other image scanning devices may be enhanced and improved.